1. Field of the Invention
The present invention relates to an improvement of an electric motor, for example, for use in electric components of an automobile.
2. Description of the Prior Art
Accompanying the increased use of electric components in automobiles, more small sized electric motors are used as actuators of electric components.
A conventional small sized electric motor is described referring to FIG. 6. As shown in FIG. 6, a permanent magnet 2 is positioned by a leaf spring 3 and fixed on an inner surface of a frame 1 by adhesive. The leaf spring 3 is calked on the frame 1 by a rivet 4. A shaft 13 of a rotor 5 is rotatively born by bearings 7. And the bearings 7 are held by the frame 1 and a cover 6. A brush holder 8 for holding a brush 9 is pinched between the frame 1 and the cover 6. Furthermore, holes 12 are provided on the frame 1 and the cover 6, through which a screw bolt 11 for fixing the above-mentioned conventional electric motor on a base of an electric component (not shown in the figure) penetrates. When an electric current is supplied to windings 5a of the rotor 5 via the brush 9 and a commutator 10, the rotor 5 starts to rotate.
In the above-mentioned conventional electric motor, it is necessary to make the frame serving as a magnetic path sufficiently thick for allowing magnetic fluxes of the magnet 2 effectively therethrough. The weight of the conventional electric motor has been unnecessarily heavy, since some parts of the frame 1 which need not serve as the magnetic path are thick.
Furthermore, hitherto the screw bolt(s) 11 is(are) used for fixing the above-mentioned conventional electric motor to a base of the electric component (not shown in the figure). The screw bolt(s) 11, however, is(are) magnetically attracted to the magnet(s) 2 when the screw bolt(s) 11 is(are) inserted into an inner space of the conventional electric motor. And thereby, the fixing process of the conventional electric motor is very difficult.